The proposed work combines mutant and biochemical analysis to localize the genes for ribosomal proteins in the eucaryote Drosophila melanogaster. The evolution of ribosomal proteins within the genus Drosophila will be investigated by 1 and 2 dimensional polyacrylamide gel electrophoresis. Tryptic peptide analysis, on one or two of the invariant ribosomal proteins from three species will be carried out to measure the sensitivity of our electrophoretic system in detecting mobility variation. Studies on the coordinate regulation of ribosomal RNA and protein synthesis will be carried out using drugs (5-Fluorouridine and alpha-amanatin) and mutants (temperature sensitive assembly mutants) which differentially effect either the synthesis or maturation of ribosomal RNA or protein. These studies will be carried out in embryonic Drosophila tissue culture cells. An experiment is described which utilizes the specificity of alpha-amanatin in inhibiting the mRNA like polymerase, and autoradiography of H3-uridine labelled chromosomes, to localize the map position of transfer-RNA genes.